1. Field of the Invention
The present invention relates to temperature controlled blankets and temperature controlled bedding assemblies, and more particularly, but not by way of limitation, to temperature controlled blankets and temperature controlled bedding assemblies to be operatively positioned with respect to a person for selective heating or cooling that person using a temperature controlled forced-gas convection system or a temperature controlled fluid recirculating system or a combination of both systems to enhance performance of the blankets and bedding systems.
2. History of the Prior Art
Medical care providers have long recognized the need to provide warmth and cooling directly to patients as part of their treatment and therapy. Better recoveries have been reported using cold therapy for orthopaedic patients. The benefits of warming patients undergoing surgery has been conclusively proven.
Several devices have been developed that deliver temperature controlled fluids through pads or convective thermal blankets to achieve the above purpose. Typically these devices have a heating or a cooling element, a source for the fluid, a pump for forcing the fluid through the pad or blanket and a thermal interface between the patient and the temperature controlled fluid. U.S. Pat. No. 4,884,304 to Elkins is directed to a mattress cover device which contains liquid flow channels which provide the selective heating or cooling by conduction.
Devices have also been developed for providing heat to a person in bed. Electric blankets containing electric heating elements have been used for years to warm a person in bed.
Cooling blankets have also been proposed such as the blanket disclosed in U.S. Pat. No. 4,660,388 to Greene. Greene discloses a cooling cover having an inflatable pad with plenum chambers at opposite ends thereof. Cool air is generated in a separate unit and directed to the pad and out a number of apertures on the underside of the pad and against the body of the person using the cover.
A disposable heating or cooling blanket is disclosed in U.S. Pat. No. 5,125,238 to Ragan, et al which has three layers of flexible sheeting. Two of the layers form an air chamber and the third includes a comfortable layer for contact with the patient. Conditioned air is directed toward the covered person through a multiplicity of orifices in the bottom layers of the blanket.
Several problems are inherent in the prior art devices. The prior art devices lack uniform temperature control. The temperature of the blankets closest to the machine supplying the conditioned air to the blanket is warmer or cooler than the remaining parts of the blanket depending upon whether the blanket is providing heating or cooling to the patient.
The present invention provides an improvement over the prior art blankets and bedding systems by providing an efficient uniform temperature controlled gaseous fluid for convectively heating or cooling the patient by using a liquid fluid with a significantly larger thermal capacity to uniformly heat or cool the gaseous fluid delivered to the patient. A further significant advantage of the present invention is the use of counter flow or co-flow heat exchanging principles to achieve temperature uniformity across different sections of the blanket.